Hi Andy,
This link gives step by step instructions how to configure a RPi from scratch.
https://indilib.org/support/tutorial...ete-guide.html
I run my KStars/EKOS/INDI on an Odroid and find it works well but it needs a certain amount of technical knowledge and persistence. The advantage with Stellarmate is the user interface, less steep learning curve and support, as Jasem can remote into the Stellarmate to troubleshoot difficult problems.
Let's face it it is still cheap. ASI is similar but I thought that it did not support motor focus and generally it's device support is not as wide as Stellarmate. It is also quite a bit more expensive ($269 on Bintel). However it has a nice intuitive interface.
Hope this helps
Mike